The influence of thermal modification, moisture content, frequency, and vibration direction plane on the damping of spruce wood (Picea abies) as determined by the wavelet transform method

Merhar, Miran (author), Moutou Pitti, Rostand (author)

This article analyses the main effect and interaction of thermal modification, wood moisture content, frequency, and vibration direction on the damping of spruce wood. Samples were thermally modified at three different temperatures (180 °C, 200 °C, and 230 °C) and then equilibrated at four different relative humidities (RHs) (20%, 44%, 76%, and 88%). The specimens were then freely supported and excited with a hammer to vibrate freely. Damping at the frequencies of the first three bending vibration modes for vibrations in the radial (LR plane) and tangential (LT plane) directions was determined using the wavelet transform method, which enables a decoupling of the vibration modes and thus a precise and accurate determination of the damping values. Damping increases with the wood moisture content for different modification levels, whereby the damping in the LR vibration direction plane differs from the damping in the LT vibration direction plane. For an unmodified sample and at frequency at the first vibration mode, damping in the radial plane is greater than in the tangential plane, but the relationships change with RHs, modification levels, and vibration direction planes. The dependence of damping on various factors has a strong influence on the calculation of various acoustic indicators, where damping of the wood is considered for the calculation, since damping for the same sample differs depending on the direction of vibration and the frequencies at different vibration modes.

• Language: English
• Keywords: damping factor, logarithmic decrement, natural frequency, wavelet transform
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: BF - Biotechnical Faculty
• Publication status: Published
• Publication version: Version of Record
• Publication date: 01.01.2025
• Year: 2025
• Number of pages: 17 str.
• Numbering: Vol. 16, iss. 7, [article no.] 1055
• PID: 20.500.12556/RUL-170198
• UDC: 630*8
• ISSN on article: 1999-4907
• DOI: 10.3390/f16071055
• COBISS.SI-ID: 241140227
• Publication date in RUL: 02.07.2025

Record is a part of a journal

• Title: Forests
• Shortened title: Forests
• Publisher: MDPI
• ISSN: 1999-4907
• COBISS.SI-ID: 3872166

Licences

• License: CC BY-NC 4.0, Creative Commons Attribution-NonCommercial 4.0 International
• Link: http://creativecommons.org/licenses/by-nc/4.0/
• Description: A creative commons license that bans commercial use, but the users don’t have to license their derivative works on the same terms.

Secondary language

• Language: Slovenian
• Keywords: faktor dušenja, logaritemski dekrement, lastna frekvenca, valčna analiza

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P2-0182-2019
• Name: Razvojna vrednotenja